This invention relates to a tool holder retention mechanism for retaining a tool or workpiece mounted to a retention plate which has a tool holder knob portion formed thereon. While the present invention may have applications other than the retentions of tool holders, the ensuing description will be facilitated by specific reference to the problem of providing a tool holder retention mechanism.
Substantial fabrication of manufactured parts is accomplished through rotary machine operations such as lathe work, rotary material removal devices and rotary drilling devices. In such operations either the material is mounted to a surface to rotate the material for working the material or the tool is mounted to a rotary device to work the material to a desired state.
In these operations the mounting and removal of the tools or workpiece can require a substantial amount of time. For example, in a lathe operation a substantial amount of time is taken in preparing the workpiece for mounting to the rotary material holding base. Also, the non uniformity of the mounting portion of tools requires adjustment of the tool retention mechanism in order to most securely retain the tool in the rotary portion.
Typical prior art tool retention mechanisms involve the use of a "chuck" which is formed with two or three jaw mechanisms which are movably engagable to retain a tool holder knob portion. While the "chuck" provides adjustability in securing the knob portion for rotation it creates a problem in that if a knob portion is slightly axially misaligned, there is a chance that the shaft of the knob portion will interfere with the inward radial movement of the chuck members when the chuck is tightened to hold the knob portion. Misalignment of the knob portion may result in damage to the tool or the workpiece held thereon.
Another area of tool retention mechanisms developed a device in which slidably movable jaw members were compressibly urged to engage notches formed on the end of a tool holder knob portion. An example of this type of device can be found in U.S. Pat. No. 2,485,799 Woytych. The tool retaining mechanism in Woytych shows two slidably movable jaws which engage notches formed on the end of the shaft of the tool holder knob portion. While the device in Woytych securely holds the tool holder in position, this device also requires that the tool holder be specifically radially aligned or "keyed-in" such that the tool holder jaws engage the notches formed on the end of the shaft of the tool holder knob portion. This method of securing a tool holder within the tool retention mechanism creates a problem in that since the tool holder must be specifically "keyed-in" to be engaged by the tool retention mechanism jaws, the position of the tool holder upon insertion is substantially limited.
Further, the device taught in Woytych is incapable of providing high precision tool holder centering and indexing. In Woytych the tool holder is centered by inserting a generally conical shaft into a generally cooperatively conical bore thereby generally seating the retaining knob portion in the center of the tool retention mechanism. While this device generally provides satisfactory tool holder centering, it has a problem in that any slight irregularities in the surface of the bore or the shaft could dramatically change the center of the tool holder. Additionally, indexing of the device is significantly limited to using the two notches formed on the shaft end.
In order to overcome the centering problem a coupling device has been developed as shown in U.S. Pat. No. 4,307,797 to Belansky. This tool holding device provides gear tooth coupling portions which meshedly engage to center the tool mounted to one of the coupling devices with a high degree of precision. This device, however, does not provide for an efficient method of retaining the coupling portions within a tool retention system. Currently this system uses a mounting portion such as a large threaded member which projects up through the center of one coupling portion to retain that coupling portion to a rotary device.
Manufacturing areas such as the aerospace industry require a high degree of precision in order to achieve the highly precise products which it requires. Additionally, with an increase in manufacturing activity, the aerospace industry has become more automated in its manufacturing operations. As such, many material machining operations have become automated such that workpiece and/or tools are transported to, mounted on and removed from processing machinery by automated devices. To provide greater efficiency and simplicity for the automated devices universal tool holders are desirable and in some applications required and are premounted to a workpiece for processing or are formed or mounted on the mounting end of a tool.
The universal tool holder provides many advantages which include the ability to mount a tool holder to a workpiece such that each time the workpiece is worked on it retains the same axis of rotation as when the tool holder was originally mounted to the workpiece. Further, the uniformity of a universal tool holder allows a single end effector to be used in automated equipment thereby eliminating the need to provide adjustable end effectors thereby making the programming and operation of the automated equipment much less complicated and much more efficient. Additionally, high precision demanding industries, such as aerospace require self-indexing tool holders to decrease the difficulty in positioning a tool or workpiece mounted to a tool retention mechanism.